Field emission of metal ions and microparticles

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Abstract
By applying an intense electric field to the end of a thin tungsten needle, covered with a film of molten gold, a beam of fast positive singly and multiply charged atomic and molecular Au ions and of Au microparticles is emitted from the needle tip in vacuo. When such a composite beam passes through a transverse electric field, the deflected particles form a cigar-shaped deposit on a target showing that the particles are charged and that the spot shape was distorted by a non-uniformity of the deflecting field. The absence of an undeflected deposit suggests a negligible number of uncharged beam particles. In contrast, by deflection in a transverse magnetic field B the beam is split into a number of circular spots which are found to lie on a straight line. Their displacements correspond to Aunm+ (charged microparticles). From the intensity of the individual deposits the intensity of the beam components has been estimated. The fairly sharp boundaries of the circular spots indicate that the velocity distribution of each component is relatively narrow. Thus both ions and charged microparticles seem to originate from the same apex sites and to be 'released' by conservative field forces.

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